What are the common constraints in Oracle

Common constraints in Oracle maintain data integrity and consistency through specific rules. These constraints include: 1. Primary key constraints: ensure that each row has a unique ID. 2. Foreign key constraints: associate a column in a table with a column in another table. 3. Unique constraint: Ensure that column values ​​are unique and allow repetition in different rows. 4. Non-null constraint: columns are not allowed to accept null values. 5. Check constraints: Ensure that column values ​​match specific conditions or expressions.

Common constraints in Oracle

Constraints are rules used to maintain the integrity and consistency of database data. A variety of constraints are provided in Oracle to control the input and manipulation of data.

Primary key constraints

Primary key constraints define the columns in the table that uniquely identify each row. It ensures that each row has a unique value that identifies it.

Foreign key constraints

Foreign key constraints relate columns in one table to columns in another table. It ensures that foreign key values ​​in the parent table refer to existing values ​​in the child table.

Unique constraint

Unique constraint ensures that the value of a certain column or a group of columns in the table is unique. It allows duplicate values, but in different rows.

Non-null constraint

Non-null constraint forces a specific column in the table not to accept NULL values. It ensures that key information in the datasheet is complete.

Check constraints

A check constraint specifies a condition or expression that the value of a specific column must satisfy. It ensures that data complies with business rules or data quality standards.

not null constraint

The not null constraint specifies that the value of a column is not allowed to be null. It ensures that the column always contains a value.

unique constraint

The unique constraint specifies that the value of a column or a group of columns must be unique. It does not allow duplicate values ​​in the same column or column group.

default constraint

The default constraint specifies a default value for a column. If a value for this column is not specified when inserting a new row, the default value will be used.

referential integrity constraints

referential integrity constraints ensure that the value of the foreign key column refers to a row that exists in the parent table. It prevents data inconsistencies when deleting or updating records in the parent table.

Benefits of constraints

Constraints provide the following benefits:

• Maintain data integrity
• Ensure data consistency
• Improve data quality
• Simplify data operations
• Enforce business rules

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